s5-1 Complex-variable representation of stress function In chapter 2, we have proved, in plane problems, there is a stress function that is biharmonic function of position coordinates, if body force is constant, i.e Vo=O Now introduce complex variable =x tiy and 2-x=iy to replace real variable x and y , noticing az_1 =1 ax Oy az =1 77 §5-1 Complex-variable representation of stress function In chapter 2,we have proved, in plane problems, there is a stress function φ that is biharmonic function of position coordinates, if body force is constant, i.e. 0 4   = 1, i 1, i = −   =   =   =   y z x z y z x z Now introduce complex variable z= x＋iy and z＝x－iy to replace real variable x and y. Noticing